/Engine/Plugins/Editor/StylusInput/Source/StylusInput/Public/IStylusState.h
The current tilt along the X axis in degrees, normalized to the range of [-90, 90]. Defaults to (0,0) ifEStylusInputType::Tiltis not supported. A value of (0,0) means that the stylus is perfectly vertical. A positive X value means that the stylus is tilted to the right. A positive Y value means that the stylus is tilted forwards, away from the user. A value of -90 or 90 means that the pen is lying on the tablet, though in practice this isn't widely supported.
FVector2D GetTilt() const